"It's cool to be cold," says Eric Larsen. The 39-year-old explorer from Grand Marais, Minnesota, has long had a love affair with the earth's most frigid places—but in 15 years of dog mushing, adventure racing, and exploring both poles, he's seen evidence of their rapid disappearance. That's why he devoted 365 days, from November 2009 to October 2010, to his Save the Poles project, an unprecedented single-year expedition to the polar trifecta—North Pole, South Pole, and Everest. Larsen hit the South Pole first, collecting scientific data, filming a documentary, and tweeting his progress, then he headed north the following March to ski, snowshoe, and swim across the Arctic in negative-50-degree temps. His mantra, "Begin with one step," propelled him through thinning Arctic ice that bent beneath his skis and fractured around his three-man team's campsites, opening gaping holes of icy water near where they slept. From seasickness-inducing whiteouts in Antarctica to avalanches on an empty autumn Everest, Larsen and his revolving cast of teammates and Sherpas bore their share of hardships. But that wasn't the whole story. "A big part of the experience is the jaw-dropping awe that these places exist," he says. "But it's countered with a dose of reality, because I could see that the character of the ice had changed dramatically. It's a jumble of emotions." Witnessing firsthand the retreat of Himalayan glaciers, which supply more than half the drinking water to 40 percent of the world's population, Larsen was reminded that, though the planet's ice may be losing its integrity, we can't afford to compromise our own. "We have to take that first step to learn and practice skills for solving environmental problems," he says. "Inaction is not an option."